\documentclass{article}
%\usepackage{pgfplots}
%\pgfplotsset{compat=newest}
%\pgfplotsset{plot coordinates/math parser=false}
\usepackage{setspace,subfigure}
\usepackage{tikz}
\usetikzlibrary{plotmarks}
\usetikzlibrary{lindenmayersystems}
\usetikzlibrary{decorations.pathmorphing}
\usepackage{geometry}
\geometry{verbose=false,papersize={4.5in,3.5in},body={4.5in,3.5in},marginratio={4:3, 2:3}}% marginratio={horizontal ratio,verticalratio}
\begin{document}
\thispagestyle{empty}
\null\vspace{-10pt}
\hspace{-10pt}
\begin{tikzpicture}[x=0.03cm,y=.02cm,font=\Large]
\draw (100,0) -- coordinate (x axis mid) (400,0);
\draw (100,0) -- coordinate (y axis mid) (100,350);
\foreach \x in {100,200,...,400}
     	\draw (\x,1pt) -- (\x,-3pt)
		node[anchor=north] {\x};
\foreach \y in {0,50,...,350}
     	\draw (101,\y) -- (97,\y) 
     	node[anchor=east] {\y};
\node[below=0.6cm] at (x axis mid) {Radius $R$, \% of $R_{\mathrm{min}}$};
\node[rotate=90, above=1cm] at (y axis mid) {Skeleton nodes $(N=400)$};
\draw[smooth] plot[] file{k1.txt};
\draw[smooth] plot[] file{k5.txt};
\draw[smooth] plot[] file{k10.txt};
\draw[smooth] plot[] file{k15.txt};
\draw[smooth] plot[] file{k20.txt};
\draw[smooth] plot[] file{k25.txt};
\draw[smooth] plot[] file{k30.txt};
\draw[smooth] plot[] file{k35.txt};
\draw[smooth] plot[] file{k40.txt};
\draw[smooth] plot[] file{k35.txt};
\end{tikzpicture}
\end{document}
